newbie 1390t getting misdirected

this is my 1st gps, beside the vz navigator i've used on my blackberry. seems like it regularly misleads me on known routes, whereas the cell app used to be fine. i live on a small lake, which has a main perimeter road to get in/out of the community. my attempts to practice using the unit will have me start from home with entering the address to where i am going. the unit always takes me out to the perimeter road, until just before the exit of the perimeter road to town streets, and always wants me to turn off of this route onto a back street running parallel. this is bizarrely illogical. the back road curves toward the lakefront properties it accesses and cannot be shorter (even inches!) than the perimeter road. what am i doing wrong or what is wrong? i avoid using the unit because i don't want this frustration. any help/ideas? thanks :confused: